3,710 research outputs found
Particle decay in false vacuum
We revisit the problem of decay of a metastable vacuum induced by the
presence of a particle. For the bosons of the `master field' the problem is
solved in any number of dimensions in terms of the spontaneous decay rate of
the false vacuum, while for a fermion we find a closed expression for the decay
rate in (1+1) dimensions. It is shown that in the (1+1) dimensional case an
infrared problem of one-loop correction to the decay rate of a boson is
resolved due to a cancellation between soft modes of the field. We also find
the boson decay rate in the `sine-Gordon staircase' model in the limits of
strong and weak coupling.Comment: 19 pages, 2 figure
Metastable anisotropy orientation of nematic quantum Hall fluids
We analyze the experimental observation of metastable anisotropy resistance
orientation at half filled quantum Hall fluids by means of a model of a quantum
nematic liquid in an explicit symmetry breaking potential. We interpret the
observed ``rotation'' of the anisotropy axis as a process of nucleation of
nematic domains and compute the nucleation rate within this model. By comparing
with experiment, we are able to predict the critical radius of nematic bubbles,
. Each domain contains about electrons.Comment: 10 pages, 8 figures, final version as will appear in PR
Degenerate Domain Wall Solutions in Supersymmetric Theories
A family of degenerate domain wall configurations, partially preserving
supersymmetry, is discussed in a generalized Wess-Zumino model with two scalar
superfields. We establish some general features inherent to the models with
continuously degenerate domain walls. For instance, for purely real
trajectories additional "integrals of motion" exist. The solution for the
profile of the scalar fields for any wall belonging to the family is found in
quadratures for arbitrary ratio of the coupling constants. For a special value
of this ratio the solution family is obtained explicitly in terms of elementary
functions. We also discuss the threshold amplitudes for multiparticle
production generated by these solutions. New unexpected nullifications of the
threshold amplitudes are found.Comment: 21 pages, LaTeX, 3 figures using epsf.st
New bounds on the neutrino magnetic moment from the plasma induced neutrino chirality flip in a supernova
The neutrino chirality-flip process under the conditions of the supernova
core is investigated in detail with the plasma polarization effects in the
photon propagator taken into account, in a more consistent way than in earlier
publications. It is shown in part that the contribution of the proton fraction
of plasma is essential. New upper bounds on the neutrino magnetic moment are
obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova
core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from
the limit on the averaged time of the neutrino spin-flip. The best upper bound
on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to
7.Comment: 19 pages, LaTeX, 7 EPS figures, submitted to Journal of Cosmology and
Astroparticle Physic
Neutrino electromagnetic properties and new bounds on neutrino magnetic moments
We give a brief outline of possible neutrino electromagnetic characteristics,
which can indicate new physics beyond the Standard Model. Special emphasis is
put on recent theoretical development in searches for neutrino magnetic
moments.Comment: 4 pages, to appear in J. Phys.: Conf. Ser. (2012), based on the talk
presented at the XII International Conference on Topics in Astroparticle and
Underground Physics (TAUP 2011), Munich 5-9 September 201
Heavy ion collisions: Correlations and Fluctuations in particle production
Correlations and fluctuations (the latter are directly related to the
2-particle correlations) is one of the important directions in analysis of
heavy ion collisions. At the current stage of RHIC exploration, when the
details matter, basically any physics question is addressed with help of
correlation techniques. In this talk I start with a general introduction to the
correlation and fluctuation formalism and discuss weak and strong sides of
different type of observables. In more detail, I discuss the two-particle
correlations/\mpt fluctuations. In spite of not observing any dramatic
changes in the event-by-event fluctuations with energy, which would indicate a
possible phase transition, such correlations measurements remain an interesting
and important subject, bringing valuable information. Lastly, I show how radial
flow can generate characteristic azimuthal, transverse momentum and rapidity
correlations, which could qualitatively explain many of recently observed
phenomena in nuclear collisions.Comment: 8 pages, 8 figures. Invited talk at 5th International Conference on
Physics and Astrophysics of Quark Gluon Plasma, February 8-12, 2005, Salt
Lake City, Kolkata, Indi
Dirac-Neutrino Magnetic Moment and the Dynamics of a Supernova Explosion
The double conversion of the neutrino helicity
has been analyzed for supernova conditions, where the first stage is due to the
interaction of the neutrino magnetic moment with plasma electrons and protons
in the supernova core, and the second stage, due to the resonance spin flip of
the neutrino in the magnetic field of the supernova envelope. It is shown that,
in the presence of the neutrino magnetic moment in the range and a magnetic field of G
between the neutrinosphere and the shock-stagnation region, an additional
energy of about erg, which is sufficient for a supernova explosion,
can be injected into this region during a typical shock-stagnation time.Comment: 10 pages, LaTeX, 4 EPS figures, accepted to JETP Letter
Estimates with an Effective Chiral Lagrangian for Heavy Mesons
On the basis of an effective lagrangian incorporating approximate chiral
symmetry and heavy-quark spin and flavor symmetries, and by use of information
on leptonic decays, we estimate the effective coupling.Comment: UGVA-DPT 1992/07-779, BARI-TH/92-117 Revised version, September 1992,
LaTeX (style article), 7 page
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